Legal Argumentation 1 Henry Prakken March 21, 2013

What is argumentation? Giving reasons to support or criticise claims that are open to doubt logic + dialectic Often to persuade someone else rhetoric Proponent:Regarding downloading Mp3s as copying for private use is wrong Respondent: Why? Proponent: Because it makes normal commercial exploitation of music impossible Respondent: Why? Proponent: Because it’s so easy to copy, upload and download MP3s

What is argumentation? Giving reasons to support or criticise claims that are open to doubt logic + dialectic Often to persuade someone else rhetoric Proponent:Regarding downloading Mp3s as copying for private use is wrong Respondent: Why? Proponent: Because it makes normal commercial exploitation of music impossible Respondent: Why? Proponent: Because it’s so easy to copy, upload and download MP3s Respondent: But there are quite profitable ways to sell Mp3s online Proponent:Really? Respondent:Look at iTunes

Legal contexts of argumentation In court In legal consultancy In scholarly debate In public debate …

Overview of course Week 1: Basic structure of arguments Combinations of premises implicit premises Multi-steps arguments Week 2: Arguments and counterarguments Argument schemes (1) Week 3: Argument schemes (2) Evaluating arguments Discussion of homework

The structure of legal arguments

The structure of arguments: basic elements (Basic) arguments have: Premises (grounds) A conclusion A reasoning step from the premises to the conclusion Conclusion Premise 1Premise n ….. therefore

Three types of support Cumulative (all premises needed for conclusion) Alternative (one premise suffices for conclusion) S was at crime scene S’s DNA matches DNA found at crime scene Witness W saw S at crime scene P E is expert on PE says that P Aggregate (the more support the better) The offer was written The offer was made in a letter The offer was made in an

Alternative support is in fact alternative arguments The offer was written The offer was made in a letter The offer was made in an The offer was written

Implicit premises The offer was made in a letter The offer was written

Implicit premises The offer was made in a letter The offer was written If the offer was made in a letter or then it was written

Implicit premises The offer was made in an The offer was written If the offer was made in a letter or then it was written

Legal reasoning: three stages Determining the facts of the case Classifying the facts under the conditions of a legal rule Applying the rule

Manslaughter IntentKilled Drove 180 where max 80 Police radar Computer log file Victim died Report coroner Caused by collision Collision Report coroner Witness: “collision” Police report: “collision” Recklessness

Manslaughter IntentKilled Drove 180 where max 80 Police radar Computer log file Victim died Report coroner Caused by collision Collision Report coroner Witness: “collision” Police report: “collision” Recklessness Art. 287 CC

Manslaughter IntentKilled Drove 180 where max 80 Police radar Computer log file Victim died Report coroner Caused by collision Collision Report coroner Witness: “collision” Police report: “collision” Recklessness Art. 287 CC Causing a collision in consequence of which someone dies is killing

Manslaughter IntentKilled Drove 180 where max 80 Police radar Computer log file Victim died Report coroner Caused by collision Collision Report coroner Witness: “collision” Police report: “collision” Recklessness Art. 287 CC Driving 180 where maximum speed is 80 is consciously taking the risk of a collision, which is Recklessness

Manslaughter IntentKilled Drove 180 where max 80 Police radar Computer log file Victim died Report coroner Caused by collision Collision Report coroner Witness: “collision” Police report: “collision” Recklessness Art. 287 CC Police radars are a reliable source of information on speed

Manslaughter IntentKilled Drove 180 where max 80 Police radar Computer log file Victim died Report coroner Caused by collision Collision Report coroner Witness: “collision” Police report: “collision” Recklessness Art. 287 CC This type of computer log file is a reliable indicator of what the radar has measured

Two important features of arguments Arguments can be constructed step by step These steps often leave rules or generalisations implicit When testing arguments, they must be made explicit to reveal sources of doubt They can be unfounded They can have exceptions

Identifying missing premises: normative, not psychological Muslim extremists should be denied free speech since they preach hatred

Identifying missing premises: normative, not psychological Muslim extremists should be denied free speech since they preach hatred So you think that anyone who preaches hatred should be denied free speech?

Identifying missing premises: normative, not psychological Muslim extremists should be denied free speech since they preach hatred So you think that anyone who preaches hatred should be denied free speech? Yes.

Identifying missing premises: normative, not psychological Muslim extremists should be denied free speech since they preach hatred So you think that anyone who preaches hatred should be denied free speech? Yes. But Geert Wilders also preaches hatred, so you should deny him free speech as well.

Summary Arguments can have different combinations of premises Arguments can be constructed step by step These steps often leave rules or generalisations implicit

Next week Arguments and counterarguments Argument schemes (1)